explaining OCD

• there are genetic and neural explanations for OCD
• first degree relatives of people with OCD have a greater vulnerability of developing the disorder
• Lewis (1936) found that 37% of patients with OCD also had a parent with OCD and 21% had a sibling with OCD suggesting a genetic inherited vulnerability
• OCD is thought to be polygenic which means that its development is determined by multiple genes
• Candidate genes are ones which, through research, have been implicated in the development of OCD. These genes tend to be involved in regulating serotonin, a neurotransmitter which facilitates message transfer across synapses
• The diathesis-stress model suggests that people gain a vulnerability towards OCD through genes but an environmental stressor is also required. This could be a stressful event e.g bereavement
•  If there are low levels of serotonin then normal transmission of mood-relevant information does not take place
• Low levels of serotonin are linked to increased anxiety levels and OCD is thought to be caused by a reduction in functioning of the serotonin system
• Some cases of OCD, in particular hoarding disorder, seem to be associated with impaired decision making
• impaired decision making may be linked to abnormal functioning of the frontal lobes, which are responsible for logical thinking and making decisions
• There is also evidence to suggest an area called the parahippocampal gyrus is associated with processing unpleasant emotions. The parahippocampal gyrus functions abnormally in OCD
• Nestadt et al conducted a meta-analysis and found an OCD concordance rate of 68% in MZ twins and 31% in DZ twins
• If OCD was purely because of genetics, we would expect concordance rates to be 100% in MZ twins. As this is not the case, then it is fair to assume there must be environmental factors which also contribute to this disorder
• There is evidence from Cromer et al (2007) that the environment is very influential. OCD was more severe in patients who had experienced traumatic events in their lives, and even more severe where patients had experienced more than one event
• Supporting evidence from antidepressant studies shows that increasing serotonin levels reduces OCD symptoms, suggesting serotonin has a role in the development of OCD
• The cause and effect relationship is uncertain. Changes in the brain could be as a result of OCD rather than the cause of OCD